Using the Cone Method to Make a Half Parabolic Dish From an 8 by 4 Sheet of Corrugated Plastic

Parabolic dishes can be used to solar cook food and pasteurize water in disaster areas like Pakistan or Haiti.  Normally they are made using a petal template and then cutting 12 or more petals from a  piece of sheet material. These are then joined together to make the dish. Here is the "cone method" which is normally used to make full dishes.
I modified it because i need a half dish for an experiment.    If used to make a half dish, it seems that the cone method makes extremely good use of a 4 by 8 sheet of corrugated plastic.
It might just be that the cone method is easier than petals in this instance.
I show it here so that others can test it out and improve on what I found.
Brian